In recent years, the telecommunications industry has seen an explosive growth in the use of DTMF (i.e., touch-tone) controlled systems. These systems have typically been employed either for the purpose of providing added user convenience or accessibility to information, or to reduce or eliminate the need for human telephone operators. For example, voice messaging systems often may be accessed with use of touch-tones to enable a caller to retrieve his or her messages or to record outgoing greeting messages or perform other administrative tasks. Even home-based telephone answering machines now routinely provide remote access from any telephone through touch-tone control. In addition, many customer service telephone numbers present touch-tone controlled menus to the caller, where the menus can be used to efficiently provide a connection to the appropriate person or department. Moreover, touch-tones are used to control many other automated systems, such as, for example, automated banking transaction and stock quotation services. These services often enable a caller to perform an entire transaction without involving a human participant on the other side of the call.
Although the fraction of telephones without touch-tone capability (i.e., rotary or dial pulse type telephones) is small and declining in the United States, there are still a substantial number of such telephones, especially outside of the United States. Moreover, many modern touch-tone telephones--including, for example, most cordless and cellular telephones--provide the keypad in the handset, thereby making it extremely cumbersome for a user to provide the required control signals to such an automated touch-tone based system while continuing to listen to the responses from the system. Thus, the use of these automated systems with typical cordless or cellular telephones often involves frequent back and forth movement of the handset which can become quite annoying. In addition, many telephone users, even those who are not facing any of the above-mentioned limitations, would find it more convenient if they could merely speak a command, rather than having to locate and then press an appropriate key with their finger.
Meanwhile, speech recognition technology has advanced substantially over the last several years. It is now technologically straightforward to provide speaker independent speech recognition (i.e., recognition of speech from any speaker previously unknown to the system) on individual words selected from a modest vocabulary. In fact, some of the aforementioned automated systems provide such speech recognition capability, eliminating the need for the user to press touch-tone keys. On the other hand, it may still be quite a while before the vast majority of these systems will have incorporated speech recognition capability to replace (or supplement) their present touch-tone control mechanisms, since, for example, the investment required to add speech recognition capability to such a system may not be justifiable on the basis of a single individual system alone.
It would be advantageous, therefore, to provide a generalized capability enabling the user of a telephone to speak a word representing a digit (or letter) key, the "*" key (e.g., the word "star") or the "#" key (e.g., the word "pound"), and to have the corresponding DTMF signal (i.e., touch-tone) automatically generated in order to provide the required input to an arbitrary touch-tone controlled system. U. S. Pat. No. 5,402,477, issued to Michael L. McMahan and Michele B. Gammel on Mar. 28, 1995, discloses a telephone set which, inter alia, includes the capability of generating touchtone signals in response to a digit, the word "star," or the word "pound," orally spoken by the user into the handset. But to make use of this capability, it is obviously necessary that this particular specialized telephone terminal equipment as disclosed therein be available to the user. As such, the approach of U.S. Pat. No. 5,402,477 clearly does not provide a solution to the problem described above and addressed herein--namely, that many telephone calls are, in fact, currently being placed either with rotary or pulse type telephones or with touch-tone telephones whose keypads are located in the handset, and will continue to be so for the foreseeable future.